Compression-ignition internal combustion engines

ABSTRACT

A compression-ignition internal combustion engine cylinder head contains an air inlet duct having two outlets encircled by the seats of two inlet valves of a cylinder. The duct extends from a lateral head surface to one outlet and thence to the other. A single covering shield shaped as a circular segment at the commencement of the one outlet has the ends of its inner edge on a line approximately radial of the cylinder as viewed axially and inclined to the axis of the associated valve, and has its inner edge, at the closest approach thereof to the latter axis, spaced from the latter axis an amount 0.25 to 0.45 times the inner diameter of the associated valve seat.

United States Patent COMPRESSION-[GNU ION INTERNAL COMBUSTION ENGINES 2Claims, 5 Drawing Figs.

[1.8. 123/193 11, 123/30 C, 123/188 M, 123/191 R Int. Cl F011 1/04,F0113/00,F02b 3/00 Field of Search 123/188,

Primary Ex,aminerWendell E. Burns Anomey Waters, Roditi, Schwartz &Nissen ABSTRACT: A compression-ignition internal combustion enginecylinder head contains an air inlet duct having two outlets encircled bytheseats of two inlet valves of a cylinder. The duct extends from alateral head surface to one outlet and thence to the other. A singlecovering shield shaped as a circular segment at the commencement of theone outlet has the ends of its inner edge on a line approximately radialof the cylinder as viewed axially and inclined to the axis of theassociated valve, and has its inner edge, at the closest approachthereof to the latter axis, spaced from the latter axis an amount 0.25to 0.45 times the inner diameter of the associated valve seat.

PATENTED JUL 6 I971 SHEET 1 OF 2 Fig.

PATENTEUJUL slam 3,590.79?

sum 2 or 2 BACKGROUND OF THE INVENTION 1. Field of the Invention.

This invention relates to a cylinder head for a compressionignitioninternal combustion engine with fuel injection transversely to airflowcirculating about the cylinder axis. The head contains a swirl-producinginlet duct which leads from a single inlet at an outwardly facinglateral surface of the cylinder head to two curving outlets situated oneafter the other in the direction of flow of the entering air andencircled by respective valve seats for inlet valves mounted in thecylinder head. As viewed substantially at right angles to the cylinderaxis and the longitudinal axis of the duct, the duct extends arcuatelyand in a narrowing fashion towards the valve seats situated in thecylinder head underside. The commencement region, nearest to theaforementioned outwardly facing lateral surface, of the first outletleading to the first valve seat is situated nearer to that surface ofthe cylinder head bounding the end of the working space of the cylinderthan is the commencement region, nearest to this lateral surface, of thesecond outlet leading to the second valve seat. Moreover, looking in anaxial direction of the cylinder, the radially inner wall of the ductwith respect to the cylinder axis is substantially tangential to theinner peripheries of the valve seats, the radially outer wall of theduct with respect to the cylinder axis extends past the first valve seatin the region of the periphery of the working space and is substantiallytangential to the inner periphery of the second valve seat, and a singlecovering shield in the form of a segment of a circle at the commencementof the first outlet has the ends of its inner edge disposed on astraight line extending approximately radially of the cylinder axis.

2. Description of the Prior Art A cylinder head with a covering shieldat the commencement region, nearest the outwardly facing lateralsurface, of the first outlet leading to the first valve seat is knownfrom British Pat No. 587,276, which differs from the head initiallydescribed by a greatly different position and shape of the coveringshield and the first outlet, and by the relative position to one anotherof the aforesaid commencement regions. Findings on which the presentinvention is based have shown that these differences reduce the airthroughput quantity through the first inlet valve and, owing to theposition of the shield, prejudice the production of a true eddy flow inthe cylinder.

A further head is known from U.S. Pat. Ser. No. 2,318,9l4which difiersfrom the construction initially described in that the inlet duct doesnot start from one but two inlets at the lateral surface and also inthat it does not have a covering shield. These difierences give acomplicated construction of cylinder head and inlet manifold, and also aweak movement of air which is not suitable for the effective formationof fuel-air mixture in a high-speed internal combustion engine with fuelinjection transversely to the air circulating in the cylinder.

Finally, a third head is known from U.S. Pat. Ser. No. 3,330,264whichdifi'ers from the construction initially described by the existence ofcovering shields at both outlets and also in that, although the inletduct follows an arcuate course as viewed perpendicularly to the cylinderaxis and its own longitudinal axis, it does not narrow towards the valveseats when so viewed. The throughflow rates of this duct leave much tobe desired and also the intensity of the true eddy flow produced isdependent on relatively slight shapeand position differences in thecovering shields.

The invention has as an object to obviate the disadvantages of knownconstructions, i.e. to provide a cylinder head which has goodthroughflow properties, produces an intensive air turbulence in themanner of a true eddy, flow adequate for mixture formation in ahigh-speed internal combustion engine with fuel injection transverselyto the air circulating in the cylinder, and the airflow produced bywhich is also substantially insensitive to dimensional and positionvariations of the covering shield due to manufacturing tolerances.

SUMMARY OF THE INVENTION According to the present invention, there isprovided in combination, a cylinder for a compression-ignition internalcombustion engine having fuel injection transversely to airfiow aboutthe cylinder axis, a cylinder head of said cylinder,

first portions of said cylinder head defining an outwardly facinglateral surface thereof, first and second inlet valve means in saidcylinder head and spaced-apart about the axis of said cylinder, thefirst inlet valve means being nearer to said lateral surface than is thesecond inlet valve means, second portions of said cylinder head defininga bounding surface thereof bounding an end of the working space of saidcylinder, third portions of said cylinder head defining first and secondinlet valve seats for said first and second inlet valve means, fourthportions of said cylinder head defining an inlet duct having a singleinlet in said lateral surface and first and second outlets encircled bythe respective valve seats, said inlet duct extending to the firstoutlet and thence immediately to the second outlet, having an outerlateral surface which is radially outer with respect to the cylinderaxis, and having an inner lateral surface which is radially inner withrespect to the cylinder axis, and a single covering shield in the fonnof a segment of a circle disposed at the commencement of the firstoutlet and having inner and outer edges of which the inner edge isnearer to the axis of said first inlet valve means than is the outeredge, the arrangement being such that:-

,a. as viewed in an axial direction of said cylinder said inner lateralsurface is substantially tangential to the inner peripheries of saidseats and said outer lateral surface extends past the first inlet valveseat in the region of the periphery of said working space and issubstantially tangential to the inner periphery of the second inletvalve seat,

b. as viewed substantially perpendicularly to the cylinder axis and thelongitudinal axis of said inlet duct, said inlet duct curves arcuatelytowards said seats and meanwhile narrows,

c. that commencement region of said first outlet nearest to said lateralsurface is nearer to said bounding surface than is that commencementregion of said second outlet nearest to said lateral surface,

d. said inner edge extends, at an oblique inclination with respect tosaid axis of said first inlet valve means, from said commencement regionof said first outlet to said commencement region of said second outlet,and, at its closest approach to said axis of said first inlet valvemeans, is spaced a distance from this axis of between 0.25 and 0.45times the inner diameter of said first inlet valve seat, and, as viewedin said axial direction, the two ends of said inner edge are disposed ona straight line which extends approximately radially of said cylinderaxis.

Conveniently, it is possible to avoid having a very small spacing of theshield inner edge from the first inlet valve means with a givenrelatively large shield surface, which spacing would be unfavorable fromthe flow point of view, by arranging that, looking in the axialdirection of the cylinder, the covering shield is crescent-shaped withthe inner edge concave.

BRIEF DESCRIPTION OF THE DRAWING In order that the invention may beclearly understood and readily carried into effect, reference will nowbe made, by way of example, to the accompanying drawings, in which:-

FIG. I shows a vertical section through a cylinder head of acompression-ignition internal combustion engine, the section being takenon the line H of FIG. 2, which contains the longitudinal axis of an airinlet duct of the cylinder head,

FIG. 2 shbws a section taken on the line [1-11 of FIG. 1,

FIG. 3 shows a section taken on the line Ill-Ill of FIG. 2,

FIG. 4 shows a section taken on the line IV-IV of FIG. 2, and

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 4, theinlet duct leads from an inlet 1 in an outwardly facing lateral surfaceof the cylinder head to a first outlet 9 and thence, in the flowdirection of the entering air, to a second outlet 1 l of the duct.Theinlet poppet valves 5 and 6 mounted in the cylinder head 4 cooperatewith valve seats 2 and 3 encircling the outlets 9 and 1H and situated inthe undersurface 7 of the cylinder head bounding the upper end of theworking space of the cylinder. As viewed in FIG. 1, the inlet ductextends arcuately towards the valve seats 2 and 3 and meanwhile narrows.That commencement region 8 of the outlet 9 nearest to the inlet 1 andthe undersurface 7 is situated nearer to the cylinder head undersurface7 than that commencement region iii of the outlet 11 nearest the inlet 1and the undersurface 7. As viewed in FIG. 2, that lateral surface l2 ofthe inlet duct which is radially inner with respect to the cylinder axisi9 is tangential to the inner peripheries l3 and 14 of the valve seats 2and 3, while that lateral surface 15 of the inlet duct which is radiallyouter with respect to the axis 19 extends past the first valve seat 2 inthe vicinity of the periphery B6 of the cylinder working space, and istangential to the inner periphery M of the second valve seat 3. Arrangedat the commencement of the outlet 9 is a covering shield 17 which is inthe form of a segment of a circle and which, as FIG. 3 shows, emergesout of the commencement region 8 and forms a portion of the cylinderhead casting. As viewed in FIG. 2, the inner edge 18 of the coveringshield 17 extends approximately on a radius 20 from the cylinder axis19. The inner edge 18 is obliquely inclined to the axis 21 of the firstinlet valve 5. The covering shield 17 and its inner edge 18 extend fromthe commencement region 8 to the commencement region 10. At its closestapproach to the axis 2!, the inner edge 18 has a spacing a from the axis21 which amounts to 0.25 to 0.45 times the internal diameter d of thefirst valve seat 2; The covering shield 22 shown in FIG. 5 differs fromthe shield 17 by being crescent-shaped as viewed in Fit}. 5, the inneredge 23 being concave, and a chord 2d drawn from one to the other of theends of the edge 23 extends approximately in the direction of the radius2th The operation of the arrangement described hereinbefore can beexplained as follows:

The fuel is injected into the cylinder by an injection nozzle 25,arranged on, or close to, the cylinder axis 119, as several individualjets shortly before the piston reaches top dead center.

The individual fuel jets (not shown) are directed radially outwards fromthe nozzle nose at a slight inclination away from the undersurface 7. Toillustrate the formation of the fuel-air mixture, it is assumed that theair particles circulating in the cylinder must just pass through onesector between two adjacent fuel jets during the injection period of agood mixture is to be formed. It is assumed that one individual fuel jetis so blown that it approximately fills the next sector downstream andfinds there the air necessary for its combustion. Tests have shown thata specific whirling speed gives the best mixture formation for aspecific injection duration and a specific number of fuel jets. When thepiston moves downwards during the admission stroke, the cylindercontents are given, owing to the described shape and arrangement of thecovering shield 17 or tion is expressed by the mean effective pressure,exhaust smoke, specific fuel consumption, pressure curve and airutilization being optimum.

The effects of the configurations of the inlet duct and the coveringshield 1'7 or 22 can be explained as follows:

From an open poppet valve, the air flows approximately in the directionof the seat surface i.e. obliquely downwards. If an inlet duct which iscoaxial with the valve axis leadsto this valve, the speed and directionof the air entering the cylinder are identical over the entirecircumference of the valve. Such an airflow cannot stimulate any rotarymovement in the cylinder, since, considering the velocity vectors at thevalve circumference, the components'thercof in a transverse plane atright angles to the cylinder axis cancel one another out since they areof equal magnitude and directed oppositely to one another.

If an inlet duct of which the main direction extends transversely to thevalve axis leads to an open poppet valve, the speed distribution of theair issuing at the valve circumference is unequal, and in fact the speedof the airflowing through the valve gap is greatest where the airflowingfrom the inlet duct is subjected to the least deflection, and issmallest where it experiences the greatest deflection. Thus, in respectof the air flowing from the inlet duct, the velocity factors disposed asa continuation of the direction of flow in the inlet duct are thereforethe maxima and so also are their components in the plane perpendicularto the cylinder axis. A vectorial addition of the velocity components inthis plane gives a resultant which obliges the air situated in thecylinder to carry out a rotational movement when the valve is arranged,as usual, to one side of the cylinder axis and in the vicinity of theperiphery of the working space and when the inlet duct extendsapproximately tangentially to the periphery of the working space. If thetransverse components of the velocity vectors of all the flow lines inthe inlet duct shortly before reaching the valve seat are addedvectoriaily, a resulting transverse component is obtained which extendsin the direction of the longitudinal axis of the inlet duct.Thedirection of this resulting transverse component coincides with thedirection of the resultant of the transverse components of the velocityvectors at the valve circumference. This means that the direction of theaxis 26 in the region shortly before the valve seat 3 deter- 22 and ofthe inlet duct, particularly the second outlet 11, a

circulating motion about the'cylinder axis 19, which is maintainedduring the following compression stroke. The requirement that thecirculating air particles should just travel through the sectors betweenthe individual fuel jets during the duration of injection is met by aso-called true eddy, wherein the speed of the'air particles at theperiphery 16 is greater than in the vicinity ofthe cylinder axis 19.This is achieved by the arrangement of the covering shield 17 or 22, andby the form of the inlet duct, in particular the second outlet H, whichhas the result that the airflowing into the cylinder is forced outwardsagainst the periphery 16. The optimum mixture formamines the maindirection of the airfiowing from the valve 6.

An identical but more intensive effect can be obtained by a coveringshield arranged near the valve seat. In this case the speed of the airat the portions of the valve circumference masked by the covering shieldis greatly reduced owing to the turbulence losses produced by thecovering shield. The

velocity vectors at the covered portions of the valve circumference andtherefore their components in the transverse plane are much smalier thanat the noncovered circumference. By vectorialaddition of all transversecomponents there is obtained a resultant in the direction of thecenterline of the covering shield, and in fact in a direction from thevalve axis 21 towards the noncovered circumference. The airflowingthrough the outlet 9 is therefore obliged to take this direction, whichin the present case coincides with the line ill-Ill as viewed in FIG. 2.

An effective air inflow into the cylinder, i.e. an air inflow directedappropriately for stimulating the necessary true eddy flow and of anadequate strength, not only requires an appropriate shape and positionof the inlet duct and the covering shield, but also requires anaccelerated flow in the region of the outlets 9 and i i as free fromloss anddetachment as possible. This requirement is met by the narrowingcross-sectional course of the outlet ill, and the arrangement of thecovering shield 17, which leads the airflow into the outlet 11 withoutsubstantial turbulence formation. The flow about the coveringshield tothe valve seat 2 is in fact not turbulence-free, but the airflowissuingfrom the valve 5 would not be able to contribute to producing thenecessary true eddy flow without the directing effect of the shield 17.The inclined position of the inner edge 18 and the indicated values forthe spacing a, however, have the effect that the turbulence losses arewithin acceptable limits having regard to the desired overall result.

lclaim:

1. In combination, a cylinder for a compression-ignition internalcombustion engine having fuel injection transversely to airflow aboutthe cylinder axis, a cylinder head of said cylinder, first portions ofsaid cylinder head defining an outwardly facing lateral surface thereof,first and second inlet valve means in said cylinder head andspaced-apart about the axis of said cylinder, the first inlet valvemeans being nearer to said lateral surface than is the second inletvalve means, second portions of said cylinder head defining a boundingsurface thereof bounding an end of the working space of said cylinder,third portions of said cylinder head defining first and second inletvalve seats for said first and second inlet valve means, fourth portionsof said cylinder head defining an inlet duct having a single inlet insaid lateral surface and first and second outlets encircled by therespective valve seats, said inlet duct extending to the first outletand thence immediately to the second outlet, having an outer lateralsurface which is radially outer with respect to the cylinder axis, andhaving an inner lateral surface which is radially inner with respect tothe cylinder axis, and a single covering shield for said cylinder headin the form of a segment of a circle disposed at the commencement of thefirst outlet and having inner and outer edges of which the inner edge isnearer to the axis of said first inlet valve means than is the outeredge, the arrangement being such that:

a. as viewed in an axial direction of said cylinder, said inner lateralsurface is substantially tangential to the inner peripheries of saidseats and said outer lateral surface extends past the first inlet valveseat in the region of the periphery of said working space and issubstantially tangential to the inner periphery of the second inletvalve seat,

b. as viewed substantially perpendicularly to the cylinder axis and thelongitudinal axis of said inlet duct, said inlet duct curves arcuatelytowards said seats and meanwhile narrows,

c. that commencement region of said first outlet nearest to said lateralsurface is nearer to said bounding surface than is that commencementregion of said second outlet nearest to said lateral surface,

d. said inner edge extends, at an oblique inclination with respect tosaid axis of said first inlet valve means, from said commencement regionof said first outlet to said commencement region of said second outlet,and, at its closest approach to said axis of said first inlet valvemeans, is spaced a distance from this axis of between 0.25 and 0.45times the inner diameter of said first inlet valve seat, and, as viewedin said axial direction, the two ends of said inner edge are disposed ona straight line which extends approximately radially of said cylinderaxis.

2. A combination according to claim 1, wherein, as viewed in said axialdirection, said covering shield is crescent-shaped, said inner edgebeing concavely curved.

1. In combination, a cylinder for a compression-ignition internalcombustion engine having fuel injection transversely to airflow aboutthe cylinder axis, a cylinder head of said cylinder, first portions ofsaid cylinder head defining an outwardly facing lateral surface thereof,first and second inlet valve means in said cylinder head andspaced-apart about the axis of said cylinder, the first inlet valvemeans being nearer to said lateral surface than is the second inletvalve means, second portions of said cylinder head defining a boundingsurface thereof bounding an end of the working space of said cylinder,third portions of said cylinder head defining first and second inletvalve seats for said first and second inlet valve means, fourth portionsof said cylinder head defining an inlet duct having a single inlet insaid lateral surface and first and second outlets encircled by therespective valve seats, said inlet duct extending to the first outletand thence immediately to the second outlet, having an outer lateralsurface which is radially outer with respect to the cylinder axis, andhaving an inner lateral surface which is radially inner with respect tothe cylinder axis, and a single covering shield for said cylinder headin the form of a segment of a circle disposed at the commencement of thefirst outlet and having inner and outer edges of which the inner edge isnearer to the axis of said first inlet valve means than is the outeredge, the arrangement being such that: a. as viewed in an axialdirection of said cylinder, said inner lateral surface is substantiallytangential to the inner peripheries of said seats and said outer lateralsurface extends past the first inlet valve seat in the region of theperiphery of said working space and is substantially tangential to theinner periphery of the second inlet valve seat, b. as viewedsubstantially perpendicularly to the cylinder axis and the longitudinalaxis of said inlet duct, said inlet duct curves arcuately towards saidseats and meanwhile narrows, c. that commencement region of said firstoutlet nearest to said lateral surface is nearer to said boundingsurface than is that commencement region of said second outlet nearestto said lateral surface, d. said inner edge extends, at an obliqueinclination with respect to said axis of said first inlet valve means,from said commencement region of said first outlet to said commencementregion of said second outlet, and, at its closest approach to said axisof said first inlet valve means, is spaced a distance from this axis ofbetween 0.25 and 0.45 times the inner diameter of said first inlet valveseat, and, as viewed in said axial direction, the two ends of said inneredge are disposed on a straight line which extends approximatelyradially of said cylinder axis.
 2. A combination according to claim 1,wherein, as viewed in said axial direction, said covering shield iscrescent-shaped, said inner edge being concavely curved.